DE102018200190B4 - Microelectromechanical system with filter structure - Google Patents

Abstract

A microelectromechanical system comprises a housing having an access opening and a sound transducer structure having a diaphragm and a backplate structure, the sound transducer structure being coupled to the access port. The microelectromechanical system includes a filter structure disposed between the access port and the acoustic transducer structure and having a filter material and at least one biasing member mechanically connected to the filter material, wherein the at least one biasing member is configured to provide a stress in the filter material to provide bending deformation of the filter structure in a direction away from the backplate structure.

Description

The present disclosure relates to a microelectromechanical system, in particular a microelectromechanical system with a transducer structure. The present disclosure further relates to a MEMS with an integrated filter structure. Microelectromechanical systems (MEMS) may be manufactured in semiconductor technology and / or include semiconductor materials. These include, for example, layers or wafers comprising a silicon material, a gallium arsenide material and / or another semiconductor material. MEMS structures may comprise layer sequences comprising electrically conductive, electrically semiconducting and / or electrically poorly conducting or insulating layers in order to provide a corresponding MEMS functionality. Some MEMS structures may include acoustic transducer structures that may include, for example, a deflectable or movable membrane. Based on an electrical signal, the membrane may be deflected to provide an audible signal. Alternatively or additionally, based on an acoustic signal, a deflection of the membrane take place, whereupon an electrical signal can be provided.

In DE 10 2016 109 101 A1 There are described devices for a microelectromechanical system comprising a support, a particulate filter structure coupled to the support, and a grid.

In US 2012/0237073 A1 For example, a MEMS microphone is disclosed having a package substrate with an acoustic path therethrough that opens an interior of the device.

In EP 2 566 183A1 a MEMS microphone is described with a built-in textile protection, wherein an open microphone body having an opening with the textile protection.

In JP 2008-271426 A For example, an acoustic sensor is described that includes an electrostatic capacitive acoustic sensor chip and a circuit board. Sound holes are arranged in a thickness direction.

It would be desirable to have MEMS with a reliably operable sound transducer structure.

Embodiments provide a microelectromechanical system having a housing having an access opening. The microelectromechanical system further comprises a sound transducer structure having a membrane structure and a backplate structure. The sound transducer structure is coupled to the access opening, for example acoustically coupled. The microelectromechanical system includes a filter structure disposed between the access port and the acoustic transducer structure and including a filter material and at least one biasing member mechanically connected to the filter material, wherein the at least one biasing member is configured to provide a stress in the filter material to provide bending deformation of the filter structure in a direction away from the backplate structure. The filter structure allows water, debris and / or particulates to be kept out of the access opening to a small extent or not to the transducer structure, while allowing the spacing of the filter structure by means of the biasing element to provide low acoustic attenuation that overall a reliable operation of the sound transducer structure can be obtained.

• 1 ein schematisches Blockschaltbild eines mikroelektromechanischen Systems gemäß einem Ausführungsbeispiel;
• 2a eine schematische Seitenschnittansicht eines MEMS gemäß einem Ausführungsbeispiel, bei dem ein Gehäuse durch einen Gehäusedeckel und eine Gehäuseplatte gebildet wird;
• 2b eine schematische Seitenschnittansicht des MEMS aus 2a, bei dem ein Vorspannungselement wirksam ist, um die Filterstruktur auszulenken;
• 3a eine schematische Seitenschnittansicht eines MEMS gemäß einem Ausführungsbeispiel, das verglichen mit dem MEMS aus 2a eine veränderte Schallwandlerstruktur aufweist;
• 3b einen ausgelenkten Zustand einer Filterstrukturaus 3a gemäß einem Ausführungsbeispiel;
• 4a-h schematische Seitenschnittansichten unterschiedlicher Konfigurationen von Filterstrukturen gemäß Ausführungsbeispielen;
• 5a eine schematische Seitenschnittansicht eines MEMS gemäß einem Ausführungsbeispiel, das eine Zugangsöffnung einem Gehäusedeckel aufweist;
• 5b eine schematische Seitenschnittansicht des MEMS aus 5a in einem ausgelenkten Zustand der Filterstruktur;
• 6 eine schematische Seitenschnittansicht eines Ausschnitts eines MEMS gemäß einem Ausführungsbeispiel;
• 7a-b schematische Seitenschnittansichten von MEMS gemäß Ausführungsbeispielen, bei denen ein Ätzprozess zu unterschiedlichen Ergebnissen führt, gemäß Ausführungsbeispielen;
• 8 eine schematische Seitenschnittansicht eines MEMS gemäß einem Ausführungsbeispiel, bei dem Rückplattenstrukturen Anti-Sticking Elemente aufweisen;
• 9 eine schematische Seitenschnittansicht eines MEMS gemäß einem Ausführungsbeispiel bei dem die Filterstruktur eine Korrugation aufweist;
• 10 eine schematische Seitenschnittansicht eines Teils eines MEMS gemäß einem Ausführungsbeispiel, das als Single Backplate Konfiguration gebildet ist;
• 11 eine schematische Seitenschnittansicht eines Teils eines MEMS gemäß einem Ausführungsbeispiel, das gegenüber dem MEMS aus 10 Anti-Sticking Elemente an der Membranstruktur aufweist;
• 12 eine schematische Seitenschnittansicht eines MEMS gemäß einem Ausführungsbeispiel, das gegenüber dem MEMS aus 11 dahin gehend modifiziert ist, dass an Bereichen gegenüberliegend der Anti-Sticking Elemente Isolationselemente angeordnet sind;
• 13a eine schematische Darstellung einer Rückplattenstruktur und einer Filterstruktur gemäß einem Ausführungsbeispiel;
• 13b eine schematische Aufsicht auf eine übereinander liegend implementierte Anordnung der Rückplattenstruktur und der Filterstruktur aus 13a;
• 13c eine Detailansicht der Lochstruktur des Filterstruktur aus 13b;
• 13d eine schematische Aufsicht auf einen Ausschnitt des Filtermaterials aus 13b; und
• 14a-c schematische Verläufe von beispielhaften Auslenkungen des Filtermaterials mit unterschiedlichen Konfigurationen des Herstellungsprozesses gemäß Ausführungsbeispielen.

Embodiments will be explained below with reference to the accompanying drawings. Show it:

• 1 a schematic block diagram of a microelectromechanical system according to an embodiment;
• 2a a schematic side sectional view of a MEMS according to an embodiment, in which a housing is formed by a housing cover and a housing plate;
• 2 B a schematic side sectional view of the MEMS 2a in which a biasing element is operative to deflect the filter structure;
• 3a FIG. 2 is a schematic side sectional view of a MEMS according to an embodiment, which is compared to the MEMS 2a has a modified sound transducer structure;
• 3b a deflected state of a filter structure 3a according to an embodiment;
• 4a-h schematic side sectional views of different configurations of filter structures according to embodiments;
• 5a a schematic side sectional view of a MEMS according to an embodiment having an access opening a housing cover;
• 5b a schematic side sectional view of the MEMS 5a in a deflected state of the filter structure;
• 6 a schematic side sectional view of a portion of a MEMS according to an embodiment;
• 7a-b schematic side sectional views of MEMS according to embodiments in which an etching process leads to different results, according to embodiments;
• 8th a schematic side sectional view of a MEMS according to an embodiment in which back plate structures have anti-sticking elements;
• 9 a schematic side sectional view of a MEMS according to an embodiment in which the filter structure comprises a corrugation;
• 10 a schematic side sectional view of a portion of a MEMS according to an embodiment, which is formed as a single backplate configuration;
• 11 FIG. 2 is a schematic side sectional view of a portion of a MEMS according to an embodiment facing the MEMS. FIG 10 Having anti-sticking elements on the membrane structure;
• 12 FIG. 2 is a schematic side sectional view of a MEMS according to an exemplary embodiment that is opposite to the MEMS. FIG 11 is modified so that at areas opposite the anti-sticking elements isolation elements are arranged;
• 13a a schematic representation of a backplate structure and a filter structure according to an embodiment;
• 13b a schematic plan view of a superimposed implemented arrangement of the back plate structure and the filter structure 13a ;
• 13c a detailed view of the hole structure of the filter structure 13b ;
• 13d a schematic plan view of a section of the filter material 13b ; and
• 14a-c schematic courses of exemplary deflections of the filter material with different configurations of the manufacturing process according to embodiments.

Before exemplary embodiments are explained in more detail below with reference to the drawings, it is pointed out that identical, functionally identical or equivalent elements, objects and / or structures in the different figures are provided with the same reference numerals, so that the description of these shown in the different embodiments Elements is interchangeable or can be applied to each other.

Subsequent embodiments relate to microelectromechanical systems or structures (MEMS) comprising a sound transducer structure. For example, MEMS transducers may be formed as speakers and / or microphones configured to sense, based on an electrical drive signal, movement of a movable element, i. H. a membrane, so that a fluid is moved by the movement of the membrane, so that a sound pressure level is generated in the fluid. Compared to the speaker configuration described above, in a microphone configuration, movement in the fluid may result in deflection of the diaphragm that is detectable by a variable electrical potential and / or a variable electrical capacitance such that an electrical signal based on fluid movement can be obtained.

MEMS acoustic transducers may be manufactured using semiconductor technology and / or comprise semiconductor materials. In the embodiments described below, backplate electrodes or backplate structures of the acoustic transducer structure may stack with a diaphragm deflectable with respect to the backplate structure, the backplate electrode and the membrane being held at respective edge regions, for example via a substrate. The substrate may be, for example, an amorphous, polycrystalline or crystalline semiconductor material, such as silicon.

1 shows a schematic block diagram of a microelectromechanical system 10 according to an embodiment. The microelectromechanical system (MEMS) 10 includes a housing 12 that has an access opening 14 having. The access opening can act as an air inlet or sound inlet or air outlet or sound outlet. The MEMS 10 includes a sound transducer structure 16 that has a membrane structure 18 and a backplate structure 22 includes. In the case 12 it may be an incompletely closed structure, which may be configured, for example, to approach a fluid flow and / or an acoustic short to an environment of the MEMS 10 to complicate or prevent. The housing 12 may be formed of semiconductor material, plastic and / or metal and may be wholly or partly formed from a potting compound.

The membrane structure 18 and / or the backplate structure 22 may comprise electrically conductive materials, so that, for example, based on a capacitive evaluation of the membrane structure 18 and the backplate structure 22 a movement of the membrane structure 18 opposite the backplate structure 22 can be determined. electrical Conductive materials may be, for example, a partial material, for example gold, copper, silver, aluminum or the like and / or a doped semiconductor material.

The sound transducer structure 16 can with the access opening 14 be coupled, so that a fluid flow 24 , which can be understood as a static, quasi-static or dynamic variation in a fluid pressure or sound pressure level, through the access opening 14 towards the transducer structure 16 can get to. The fluid flow 24 can with a deflection of the membrane structure 18 causally related, especially in an operation of the transducer structure 16 as a microphone and / or speakers.

The MEMS 10 includes a filter structure 26 that is between the access opening 14 and the sound transducer structure 16 is arranged. The filter structure 26 includes a filter material 28 and at least one biasing element 32 that mechanically with the filter material 28 connected is. The biasing element 32 is adapted to a mechanical stress in the filter material 28 to produce a bending deformation of the filter structure 26 in a direction away from the backplate structure 22 provide. The mechanical connection between the filter material 28 and the biasing element 32 can be obtained, for example, by mechanical adhesion, such as by using adhesives, but can also be obtained by growing a layer of material of the biasing element on a layer of the filter material, or vice versa.

The filter material 28 may be configured to provide a barrier to portions of the fluid stream 24 represent, for example, particles and / or liquids. For this, the filter structure 26 or the filter material 28 have a hole structure whose holes have a correspondingly small opening size, for example a diameter. This allows the flow of the fluid stream 24 while keeping appropriate components of the fluid stream 24 ,

The bending deformation of the filter material 28 allows you to maintain a distance 34 based on an undeflected state of the filter material 28 , The distance 34 This can be due to an obtained deflection of the filter material 28 in a central region of the filter structure 26 refer while the filter material 28 For example, it can be firmly clamped in an edge region and may indeed have material expansions there, but under certain circumstances it may not have any deflection at least locally. By the distance 34 it will allow an acoustic attenuation of the filter structure 26 with respect to the sound transducer structure 16 is low, a good filter property is achieved and at the same time a spatial proximity between filter structure 26 and sound transducer structure 16 can be obtained, for example, by adding some, some or all of the layers comprising the membrane structure 18 , the back plate structure 22 and / or the filter material 28 be formed from a same stack.

Although the 1 is shown as the backplate structure 22 between the filter material 28 and the membrane structure 18 is arranged, it is possible without limitation in the embodiments described herein that the membrane structure 18 between the backplate structure 22 and the filter material 28 is arranged.

In other words, the filter structure protects 28 a sensor element, for example the sound transducer structure 16 before environmental influences, for example particles and / or water.

Embodiments enable protection of the sensor structure by an integrated filter structure. This total costs, processing and / or space can be kept low or reduced. The protective structure, that means the filter structure 28 can be implemented as a grid-shaped layer. The smaller their holes are made, the better and higher can be a filtering effect of the filter structure 28 are obtained against particles and / or water. At the same time, however, influences on the disturbing characteristics can be obtained, for example, by a reduction of the signal-to-noise ratio (SNR) of a microphone, which can be achieved by the backplate structure 22 , For example, can be at least partially offset by increasing the size of the holes.

2a shows a schematic side sectional view of a MEMS 20 ₁ in which the case 12 through a housing cover 12a and a housing plate 12b is formed. The housing plate 12b For example, it may be a carrier substrate for electrical leads or may include these leads, such as by the housing plate 12b is formed as a board or the like.

The access opening 14 For example, in the housing plate 12b be arranged. In addition to a sound transducer structure 16 ₁ , which may be implemented, for example, as a double backplate transducer structure in which the diaphragm structure 18 between two membrane structures 22a and 22b can be arranged, more elements within the housing 12 be arranged. For example, inside the case 12 a substrate 42 that the sound transducer structure 16 ₁ from the access opening 14 spaced, ie between the access opening 14 and the sound transducer structure 16 ₁ be arranged. Alternatively or additionally, within the housing 12 also a drive circuit 44 be arranged with the sound transducer structure 16 ₁ is electrically coupled and may be configured to provide functionality thereof. The drive circuit 44 may include an amplifier that is separate from the transducer structure 16 ₁ received electrical signals and / or signals to be supplied thereto electrically amplified.

The filter structure 26 can as an integrated filter element with respect to the MEMS 20 ₁ be understood. As shown in 2a is the biasing element of the filter structure 26 to a lesser extent active or inactive, that means the 2a shows the MEMS 20 ₁ in a state where the filter material is undeflected.

2 B shows a schematic side sectional view of the MEMS 20 ₁ in which the biasing element is effective, so that the filter structure 26 or the filter material is deflected to one compared with the representation in 2a increased distance to the backplate structure 22 b , to the back plate structure 22a and / or the membrane structure 18 exhibit.

3a shows a schematic side sectional view of a MEMS 20 ₂ compared to the MEMS 20 ₁ a modified sound transducer structure 16 ₂ having. The sound transducer structure 16 ₂ has a single backplate configuration in which the membrane structure 18 against a single backplate structure 22 can be deflected. The back plate structure 22 For example, it may be arranged such that the membrane structure 18 between the backplate structure 22 and the filter structure 26 is arranged. Alternatively, it is also possible that the backplate structure 22 between the membrane structure 18 and the filter structure 26 is arranged. Without the words "top", "bottom", "left", "right", "front" and "rear" in embodiments described herein to be limiting effect, the MEMS 20 ₂ be described so that the sound transducer structure 16 ₂ over the access opening 14 is arranged so that the membrane structure 18 over the access opening 14 with an environment of MEMS 20 ₂ is fluidically coupled.

While 3a comparable to the 2a an undeflected state of the filter structure 26 shows, shows 3b a deflected state of the filter structure 26 in which the filter structure 26 is so distracted that they compared with 3a a greater distance to the membrane structure 18 and / or the backplate structure 22 having. The deflected state of the filter material can be obtained by effective biasing elements.

Based on 4a to 4h Reference will now be made to the deflection of the filter structure 26 or the filter material 28 that on a substrate 46 , For example, can be suspended or clamped to a semiconductor substrate.

4a shows a schematic side sectional view of the filter structure in a first configuration 26a in which the filter material 28 a plurality of holes 36 _i through which the fluid flow can pass. With the filter material 28 firmly connected, for example, two biasing elements 32 ₁ and 32 ₂ Wherein, any other number of biasing elements may be used, for example, one, three or more, four or more, five or more, ten or more, for example 15 , For example, the filter material 28 be a circumferentially fixed to a substrate structure, so that a single biasing element 32 can also be arranged as a rotating element. Alternatively, a higher number can be used.

The biasing elements 32 ₁ and 32 ₂ can with the filter material 28 be mechanically fixed and be adapted to a mechanical stress in the filter material 28 to create. This can be provided for example by different thermal expansion coefficients. Alternatively or additionally, at least one of the biasing elements 32 ₁ and or 32 ₂ be configured in a different way to a mechanical stress in the filter material 28 to create. For example, a main direction of extension of the filter material 28 parallel to an x-direction, where a surface normal of the filter material 28 perpendicular thereto and parallel to one y Direction can be arranged. The biasing elements 32 ₁ and or 32 ₂ For example, they may be configured to face the filter material 28 along the x Direction to expand the mechanical stress in the filter material 28 to create. For example, the biasing elements 32 ₁ and 32 ₂ simultaneously with the filter material 28 be generated or processed so that both have a same temperature, while a substantially stress-free state between the filter material 28 and the biasing elements 32 ₁ and 32 ₂ prevails. By heating and / or cooling the stack to a different temperature, the filter material can 28 and a material of the biasing elements 32 ₁ and or 32 ₂ expand differently, so that, for example, the biasing elements 32 ₁ and 32 ₂ towards the filter material 28 enlarge and based on the mechanical connection to the filter material 28 generate the mechanical tension.

For example, the filter material 28 a silicon material and a material of the biasing elements 32 ₁ and or 32 ₂ a silicon nitride material, for example, silicon nitride (SiN) or silicon oxynitride (SiON). For example, the filter material may comprise a polycrystalline silicon material and the biasing elements 32 ₁ and or 32 ₂ having the nitride material.

4b shows a schematic side sectional view of the deflected state of the filter structure 26a in which, based on the mechanical stress, the deflection of the filter material 28 is obtained, so that the distance 34 is obtained to a back plate structure, not shown. The distance 34 can as a deflection of the filter material 28 to an undeflected state, for example, by a dashed line 38 is meant to be understood.

4c shows a schematic side sectional view of the filter structure in a second configuration 26b in which the biasing elements 32 ₁ and 32 ₂ compared to the first configuration 26a are formed to face the filter material 28 to contract so that the mechanical stress based on the contraction of the biasing elements 32 ₁ and 32 ₂ can be obtained.

While the locations of the arrangement of biasing elements 32 ₁ and or 32 ₂ compared with the 4a may be equal or comparable, allows contraction of the biasing elements 32 ₁ and or 32 ₂ a deflection of the filter material 28 and the distance 34 along the positive y-direction, while the deflection is in accordance with 4b along the negative y-direction.

The configuration 26b can be obtained, for example, by referring a reference state or stress-free state, for example, to a temperature lower than a temperature at which the deflection state is obtained, that is, the filter material 28 and the biasing element (s) 32 ₁ and or 32 ₂ heat to provide the deflection.

Although the configurations 26a and 26b are described so that the biasing elements 32 ₁ and or 32 ₂ in an edge region of the filter material 28 are arranged, other places are possible. Here, the places offer the greatest material expansion, as these to a high deflection of the filter material 28 being able to lead. Is the filter material 28 For example, firmly clamped in the edge regions, so places of great mechanical strain can be arranged adjacent thereto. The configurations 26a and 26b are shown as a possibly single vibration of the filter material 28 obtained in a central region of the filter structure 28 can be arranged. It is understood that other bending lines can be produced, for example with a higher number of deflection maxima. This also leads to a higher number of locations with large or largest elongation in the filter material 28 What the selection of the mounting locations of the biasing elements 32 ₁ and or 32 ₂ or other biasing elements.

As an alternative to locations of high or maximum elongation, it is also possible to select locations with different properties, for example locations with a large or maximum amplitude of the distance 34 ,

4d shows a schematic side sectional view of the deflected state of the filter structure 26b in which, based on the mechanical stress, the deflection of the filter material 28 is obtained.

4e shows a schematic side sectional view of the filter structure in a third configuration 26c in which a possibly single biasing element 32 in a central region of the filter material 28 is arranged and configured to expand against the filter material, as related to the 4a is described. A possible biasing element can be obtained using TEOS (tetraethylorthosilicate), although other materials compatible in particular with etching processes such as HF (fluoride hydrofluoric acid) etching process can also be used.

4f shows a schematic side sectional view of the configuration 26c in the deflected state where the distance 34 obtained from the reference state.

4g shows a schematic side sectional view of the filter structure in a fourth configuration 26d in which the biasing element 32 compared to the configuration 26c is formed to face the filter material 28 to contract to provide the mechanical stress.

4h shows a schematic side sectional view of the filter structure 4g in the fourth configuration 26d in which the filter material 28 based on the obtained mechanical stress is deflected to that through the line 38 indicated reference state the distance 34 provide.

The 4a to 4h illustrate that with a different number and / or different locations of attachment of at least one mechanical biasing elements, a deflection of the filter material 28 can be obtained. The mechanical bias can be obtained by different thermal expansion coefficients with respect to a common reference state, which may or may not necessarily describe a temperature range during manufacture. As an alternative to this concept, an actuation can also be used to obtain the mechanical stress, for example by applying a temperature, a force generated by means of an actuator, or the like.

5a shows a schematic side sectional view of a MEMS 20 ₃ compared to the MEMS 20 ₁ and 20 ₂ the access opening 14 in the housing cover 12a that is, the fluid flow 24 can from a direction, for example, referred to as the top direction toward a transducer structure 16 ₃ reach. The sound transducer structure 16 ₃ can be formed as single backplate or dual backplate configuration. In the case of a single backplate configuration, the sound transducer structure 16 ₃ the back plate structure 22 based on the membrane structure 18 closer to the access opening 14 or closer to the housing plate 12b respectively. The 5a shows the MEMS 20 ₃ in an undeflected state of the filter structure 26 ,

5b shows a schematic side sectional view of the MEMS 20 ₃ in a deflected state of the filter structure 26 , The filter structure 26 is deflected so that the distance from the back plate structure 22 and / or the membrane structure 18 increased.

The features associated with the MEMS 20 ₁ . 20 ₂ and 20 ₃ have been described, can be combined with each other. In particular, a configuration of the housing may be a position of the access opening 14 and a configuration of the transducer structure with respect to single backplate and dual backplate as well as an orientation of the backplate structure in the case of a single backplate configuration can be interchangeable.

6 shows a schematic side sectional view of a section of a MEMS 50 according to an embodiment. For example, only a side section of the MEMS is 50 shown, that is, to a right edge of the image, the structures shown may extend. Further, the MEMS 50 for example, formed so that the membrane structure 18 between two backplate structures 22a and 22b is arranged.

The MEMS 50 For example, it may be formed of a layer stack having a plurality of layers and from which the backplate structures 22a and 22b as well as the membrane structure 18 in a central region, somewhat through a chemical or mechanical etching process, to the functionality of the MEMS 50 to enable. For example, the backplate structures 22a and 22b as well as the membrane structure 18 in the edge region of the semiconductor substrate 46 be held, that is, to be firmly clamped to it, wherein the semiconductor substrate 46 multiple layers 46 ₁ to 46 ₄ can have. Alternatively, the semiconductor substrate may be formed with a single layer, two or more layers, three or more layers, or five or more layers, for example, ten, twenty, or even more.

The substrate material 46 For example, a semiconductor material may include or include, for example, silicon. The semiconductor material can be obtained, for example, by using TEOS (tetraethyl orthosilicate). Such a resultant material of the semiconductor substrate layers 46 to 46 _i may be electrically insulating and, for example, comprise and be formed from a silicon oxide material. The use of nitride as insulating material of the layers 52 ₁ to 52 ₄ allows relief of stress points 74 ₁ and or ₂ which damage the semiconductor material of the layer upon movement of the corresponding structure 28 or 48 could cause. In other words, hotspots (stress points) 74 protected by tensile SiN. The insulating material can be arranged as SiN taper, wherein the use of silicon nitride material a large deflection of the filter material 28 because it can provide a high tensile stress in the silicon material.

The backplate structures 22a and 22b as well as the membrane structure 18 can be electrically conductive, allowing a movement of the membrane structure 18 opposite the back plate structures 22a and or 22b can be detected by evaluating electrical potentials or capacitance values, or by applying electrical potentials or charge carriers, a movement of the membrane 18 can be obtained. The backplate structures 22a and or 22b can, compared with the membrane structure 18 to be deflected to a small extent. For example. may be in response to a comparably large force acting on the membrane structure 18 and the backplate structures are effective, a path length of deflection of the backplate structures may be smaller by a factor of less than 0.1, less than 0.05, or less than 0.01.

For example, the backplate structures 22a and 22b itself be formed as multilayer elements and, for example, an electrically conductive layer 48 include, by one or several insulating layers 52 ₁ and or 52 ₂ is covered on one or both main sides, in order to avoid a short circuit in a mechanical contact with another electrically active structure. Likewise, the back plate structure 22b an electrically conductive layer 48 ₂ comprise, for example, on both sides with an electrically insulating layer 52 ₃ or. 52 ₄ is covered.

The electrically conductive layers 48 ₁ and or 48 ₂ may comprise a doped semiconductor material and / or a metal material. The insulating layers 52 ₁ to 52 ₄ For example, they may include an oxide material or a nitride material, such as silicon nitride or silicon oxynitride.

The membrane structure 18 For example, as an electrically conductive layer 48 ₃ be formed. Optionally, the membrane structure 18 also be covered on one side or on both sides at least in places by an electrically insulating layer, wherein the electrical insulation to the backplate structures is preferably arranged on the backplate structures themselves, to a low mass of the membrane structure 18 to enable.

The layer stack or the MEMS 50 can the filter structure 26 which is formed, for example, as a bimorph structure. That means in a bias area 54 for example, in an edge region of the MEMS 50 is arranged, is the filter material 28 with the biasing element 32 at least in places or completely covered. The filter material 28 may be formed electrically conductive and include, for example, the same material as the conductive layers 48 ₁ and or 48 ₂ and / or a membrane material of the membrane structure 18 that means the layer 48 ₃ , The biasing element 32 can on one of the backplate structure 22b opposite side of the filter material 28 be arranged.

For example, this is MEMS 50 configured the backplate structure 22b between the access opening 14 and the membrane structure 18 is arranged. Such a configuration can cause particles 56 ₁ and or 56 ₂ of the fluid 24 to the back plate structure 22b while the backplate structure 22a is applied to a lesser extent or to no extent with particles. The filter structure 26 can now be used to the particles 56 ₁ and or 56 ₂ from the back plate structure 22b hold. This allows for openings or holes 58 the backplate structure can be formed comparatively large, since they are at least partially exempted from a functional requirement of particle removal. This feature may be different from the filter structure 26 be provided so that openings or holes 62 the filter structure 26 may be formed with a smaller dimension than the holes 58 , It can be seen that the filter structure 28 an acoustic behavior of the sound transducer device influenced. At the same time, known process parameters can be maintained, in particular layer thicknesses of the substrate 46 ,

According to one embodiment, a diameter or a comparable dimension of the openings 62 , which determines the particle size for which the filter structure 26 is mechanically impermeable, a dimension that is smaller than the distance 34 , so through the filter structure 26 passing particles are small enough to make simultaneous contact with the filter structure 26 and the backplate structure 22b to prevent. The size of the holes 62 can be chosen so that particles passing through the holes 62 pass, leading to no significant interference when placed in an area between the back plate 22b and the membrane structure 18 reach.

For example, a layer thickness 64 the substrate layer 46 ₃ between the backplate structure 22b and the filter structure 26 with a correspondingly corresponding distance between the backplate structure 22b and the filter structure 26 be low in the edge region and, for example, have a value of at least 0.5 .mu.m and at most 3 .mu.m, at least 1 .mu.m and at most 2.5 .mu.m or at least 1.5 .mu.m and at most 2.2 .mu.m, for example 2 microns. The distance 34 can be based on the biasing element 32 have at least 6 microns, at least 8 microns or at least 10 microns. The distance 34 can be used as an enlargement of the layer thickness 64 provided spacing can be and, for example, at least have a double value as the layer thickness 64 , At least a value of 2.5, at least a value of 3 or even more, for example. 5. The deflection by the biasing element allows obtaining a high distance 34 while avoiding deposition of correspondingly high layer thicknesses on the edge. In other words, the backplate structure 22b in the border area 68 the back plate structure 22b the distance 64 to the filter structure 26 and in the middle area 66 the distance 34 , The distance 34 may have a value of at least a double value, at least a triple value, at least a quadruple value but also at least a five-fold value and, for example, a value of at least 6 microns, at least 8 microns or at least 10 microns.

The middle area 66 can be used as the area of the membrane structure 18 be understood, which is configured for a deflection of the same. The border area 68 can be understood as a clamping area or holding area, in which a Anchoring the respective layers can take place and / or of an exposure of the individual substructures 22a . 18 . 22b and 26 remains.

A base layer 72 of the layer stack may, for example, be a silicon layer, for example the remainder of a silicon wafer, on which the further layers have been produced or arranged. The silicon material of the base layer 72 For example, it may be comparatively sensitive to etching when an etch sensitivity of the semiconductor substrate 46 is used comparatively. For example, an exposure of the individual layers can take place from one direction in which the access opening 14 is arranged so that the layers 46 ₁ . 46 ₂ . 46 ₃ and 46 ₄ in the order mentioned may have an increasingly longer residence time in an etching material. Therefore, these layers can undergo increasing removal in the order named, so that the between the backplate structure 22b and the filter structure 26 in the border area 68 arranged insulation material of the substrate 46 in the area of the filter structure 26 is eroded to a greater extent, so that the filter structure in an area higher extent of the insulating material of the semiconductor substrate 46 is exposed as the backplate structure 22b , This may also mean that the insulator material is one of the backplate structure 22b facing side of the filter structure 26 covered in area to a greater extent than one of the back plate structure 22b opposite side. If a configuration of the layer sequences is changed, for example, that the filter structure 26 adjacent to the backplate structure 22a is disposed, the insulating material may cover the backplate structure facing side of the filter structure to a lesser extent than the side facing away from the backplate structure side. This can be understood in a simplified way that the retaining oxide of the layers 46 can be removed in both sides in a higher extent.

The filter structure 26 can be formed so that the filter structure 26 for particles 56 with a certain particle diameter and above it is mechanically impermeable. For example, the filter structure 26 be formed so that it is mechanically impermeable to particles having a diameter of at least 6.5 microns, at least 6 microns or at least 5.5 microns.

As it is based on the 7a and 7b is shown, the amplitude of the distance 34 a degree or extent of coverage of the filter material 28 with the insulating material of the semiconductor substrate 46 ₃ be at least partially determined, wherein the side of the filter material can be taken into account that the biasing element 32 turned away. For example, this may be for the MEMS 50 through the layer 46 ₃ be fulfilled. In one area 76 in which the filter structure is opposite to the biasing element 32 from the semiconductor substrate 46 is covered, may be a deflection of the filter material 28 by the biasing element 32 be reduced or prevented. Outside the range 76 toward the center region, the biasing element can 32 a deflection of the filter material 28 generate the distance in the center area 34 to the back plate structure 22a to create. This allows the width of the exposed bimorph region, that is, an extension of an area 78 within which the filter structure can deform and within which the deformation element 32 can be independent of a position of a Bosch cavity, which may for example denote those areas within which the base layer 72 Will get removed. A difference 82 between the removal of the base layer 72 in a MEMS manufactured in a first cycle 50a and a MEMS manufactured in a second cycle 50b or a difference between two simultaneously manufactured MEMS 50a and 50b can have a value of up to ± 20 microns to each other and thus provide low precision. Execution examples allow for at least partial independence from this parameter, since the deflection of the filter structure 26 from a removal of the semiconductor material 46 is determined what can be removed with high precision, such as by an etching process. This can be an exact adjustment of the distance 34 and thus enable high reproducibility.

8th shows a schematic side sectional view of a MEMS 70 in accordance with embodiments described herein wherein the backplate structures 22a and 22b Have anti-sticking elements 84. The anti-sticking elements 84 ₁ and 84 ₂ the back plate structure 22a can in the direction of the membrane structure 18 be directed. The anti-sticking elements ₃ and 84 ₄ can move in the direction of the filter structure 26 be directed. Optionally, the membrane structure 18 also anti-sticking elements 84 ₅ and or 84 ₆ that are in an area between the membrane structure 18 and the backplate structure 22b protrude. Anti-sticking elements 84 allow surface contact of these elements to be avoided when mechanical abutment of two adjacent elements occurs and, instead, contact is primarily in a region of the anti-sticking elements 84 takes place, so that adhesion is prevented. The membrane structure 18 For example, it is movable along the y-direction and may be configured to engage with the backplate structures during manufacture and / or operation 22a and 22 to come into mechanical contact. A sticking (sticking) can be done by the anti-sticking elements 84 be reduced or prevented. As it is in the Related to the MEMS 70 Anti-sticking elements can be shown in all intermediate areas between the elements 22a and 18 . 18 and 22b and 22b and 26 protrude. A location of the attachment of the anti-sticking elements may be at least influenced, for example, by a sequence of layers which is used for the production of the MEMS. For example, the anti-sticking elements 84 similar to a stalactite may be formed so that they are introduced into a later or top deposited layer and (at least during production) facing down. That means the anti-sticking elements ₃ and 84 ₄ at the back plate structure 22b and / or the filter structure 26 can be arranged. Alternatively or additionally, the anti-sticking elements can be arranged on any structure.

The filter structure 26 can be brought to the same potential as the backplate structure 22b , This enables the reduction or prevention of parasitic effects according to which the filter structure 26 capacitive with the membrane structure 18 acts. Regardless, electrical isolation may occur between the backplate structure 22b and the filter structure 26 be arranged and, for example, through the insulation layers 52 ₂ and 52 ₄ It also implements the anti-sticking elements 84 are formed. The electrical insulation makes it possible to avoid a short circuit, which despite the same potential can be unwanted. Although the filter material may also be embodied as electrically non-contacted (floating), it may alternatively be applied to an identical or similar potential, such as the membrane structure 18 ,

Although only two anti-sticking elements are the structure 22a . 18 and 22b It should be noted that anti-sticking elements can be arranged in a high number, e.g. Each with more than two, more than five, more than ten, more than 50 or more than 100.

9 shows a schematic side sectional view of a MEMS 80 according to an embodiment, which may be formed similar to the MEMS 70 , where the arrangement of anti-sticking elements 84 is optional and can be omitted. The filter structure has a corrugation or corrugation 86 on, the one or more path extensions 88 ₁ and or 88 ₂ may be formed in the course of the deflection of the filter structure 26 along the y Direction a way extension perpendicular thereto, approximately along the x Direction. In this case, a scope of the travel extension can be adjusted such that it provides at least the additional extent due to the deflection of the filter structure 26 can be claimed, in which case tolerance ranges of ± 50%, ± 30%, or ± 10% can be used. For example. can derive the additional deflection at an exemplary membrane radius of 400μm and a deflection of 8μm as a new membrane radius $$\sqrt{{400}^2+{\mathrm{<figure-callout\; id="2"\; label="8th"\; filenames="DE102018200190B4\_0005.png,DE102018200190B4\_0010.png"\; state="\{\{state\}\}">8th</figure-callout>}}^2}=400.08$$

Thus, an additional path length of 0.08 microns can be provided, which additional Wwglänge can be acted upon above-mentioned tolerances. One design criterion may be that corrugation makes the filter layer softer and thus more elastic. The more displacement that can or should be provided in later operation, the more length / extent can be provided by corrugation. Based on a geometry of the filter structure 26 and based on a deflection of the filter material for establishing the distance 34 For example, the corrugation may provide a travel extension having a value of, for example, at least 0.1 μm, at least 0.2 μm, at least 1 μm, at least 2 μm, or another geometry-dependent value.

The corrugation 86 can accordingly act as a length compensation, which provides the path length taken up by the deflection of the filter structure. The corrugation 86 can act like a spring running along the x- Direction perpendicular to the deflection soft is formed.

In other words, the corrugation can act like a spring, its elasticity high and its rigidity at least along the x Direction is small, to the deflection of the filter material 28 to increase or enable.

10 shows a schematic side sectional view of a portion of a MEMS 90 According to an embodiment, which is formed as a single backplate configuration, wherein the filter structure 26 is arranged so that the membrane structure 18 between the backplate structure 22 and the filter structure 26 is arranged. This may be, for example, a configuration in accordance with the MEMS 20 ₂ act. The back plate structure 22 Can one or more anti-sticking items 84 respectively. The membrane structure 18 and / or the filter structure 26 For example, they may be formed in the absence of anti-sticking elements.

11 shows a schematic side sectional view of a portion of a MEMS 100 that is opposite to the MEMS 90 also anti-sticking elements 84 ₂ and ₃ at the membrane structure 18 that is in an area between the membrane structure 18 and the filter structure 26 protrude. Regarding the MEMS 90 and 100 can the access opening the housing, for example, adjacent to the filter structure 26 be arranged. Alternative embodiments provide that the backplate structure 22 between the membrane structure 18 and the filter structure 26 is arranged. Alternatively or additionally, it is conceivable that the filter structure 26 is arranged so that it is attached to one of the membrane structure 18 opposite side of the filter structure 22 is arranged. For example, the filter structure can be arranged in the image direction at the top and optionally have, for example, anti-sticking elements.

12 shows a schematic side sectional view of a MEMS 110 according to an embodiment, which is opposite to the MEMS 100 is modified to that on the filter structure 26 in areas with the membrane structure 18 , especially the anti-sticking elements 84 ₂ and ₃ the same can come into mechanical contact, insulation elements 92 ₁ and 92 ₂ are arranged, for example, have the same or similar material, as the biasing element 32 , This means the insulation material of the insulation elements 92 may comprise a silicon nitride material. Just as it is for example in connection with the MEMS 70 For example, anti-sticking elements define the backplate structure 22b or the membrane structure 18 Contact areas of the filter structure 26 in which a mechanical contact with the backplate structure or membrane structure can take place. At least in the contact areas, the insulating material may be arranged, for example by insulation elements 92 or by coating the anti-sticking elements with a layer 52 , The insulation elements 92 may also be understood as a landing pad, occupying a total area of not more than 2% of the filter structure, not more than 1.5% or not more than 1% of the filter structure.

13a shows a schematic representation of a backplate structure and a filter structure according to an embodiment. The back plate structure 22 and the filter structure 28 Both can each as a hole structure with a variety of holes 62 or. 58 be formed. According to one embodiment, the holes 62 and or 58 be formed as hexagons, with other shapes, such as triangles, squares, pentagons, heptagon or any other n-corner and / or irregular polygons can be implemented up to round or oval openings. The holes 58 can have an opening 94 which, for example, determines a size which particles may have, below which they have the filter structure 28 can happen. Similarly, the holes can 62 the back plate structure 22 openings 96 or size of the holes 62 , which determines a corresponding particle size, up to the particle, the backplate structure 22 can happen. Between adjacent holes 58 can walkways 98 may be arranged, which may have an axial extension length and may have a lateral extent, which may also be referred to simply as width. The axial length of the web 98 can be in accordance with the opening size 94 be elected. A web width of the webs 98 In this case, it may have a value of at least 1 μm and at most 7 μm, at least 1.7 μm and at most 5 μm or at least 1.2 μm and at most 2 μm, for example 1.4 μm. The openings 94 , which can also be understood as filter holes, can be smaller than the openings 62 which can also be understood as back plate holes. According to one embodiment, the filter structure has an acoustic attenuation of sound transmitted or received through the access opening of at most 2 dB, at most 1.6 dB or at most 1.2 dB, about 1.0 dB. In other words, a back plate material of the back plate structure 22 the back plate holes 62 have their dimensions 96 larger than the dimension 94 the filter holes 58 , Stege 102 The backplate structure can be the same or at least similar to the webs 98 the filter structure.

13b shows a schematic plan view of a superimposed implemented arrangement of the back plate structure 22 and the filter structure 28 , According to one embodiment, the backplate structure 22 and / or the filter material 28 the filter structure 26 formed as a hole structure. The holes of the hole structures may have any geometry, for example elliptical, round, polygonal or according to a free-form surface. Although the back plate structure 22 and the filter structure 26 are shown as having hexagonal holes, at least one of the two structures may be different therefrom. In addition to mutually different opening sizes, different geometries of the backplate structure can also be used 22 and the filter structure 22 be implemented.

The backplate structure can, for example, in the positive y-direction, starting from the filter structure 28 be arranged so that the fluid flow, the first the filter structure 28 happens and then to the back plate structure 22 gets cleared with respect to particles passing through the filter holes 58 not get through. This allows the backplate holes to be compared with known backplate structures 62 can be larger and therefore may have a lower acoustic attenuation, which is the compensation of a supposedly additional acoustic attenuation through the filter structure 28 can counteract. For example, the opening 96 a value of at least 10 microns, at least 12 microns or at least 14 microns or be greater. This allows for backplate transparency, which means a Area fraction of the openings on the total area, of at least 50%, at least 60% or even at least 70% or more.

According to one embodiment, the backplate structure 22 and the filter structure 28 doing so staggered to each other, that both the webs 98 as well as their connection points as well as the webs 102 as well as their connection points at a deflection of the back plate structure 22 and / or the filter structure 28 such that a contact between the two structures takes place, at most to a small extent parallel or congruent to each other, so as to avoid a large-area contact. To a large or complete extent, there is contact between the backplate structure 22 and the filter structure 28 in the area of the bridges 98 and 102 instead of being avoided in the area of junctions or crossroads.

As it is based on 13c is further described, the webs have 98 each connection points 104 on, where a respective number, for example three bars 98 meet. Similarly, the webs 102 at joints 106 meet. According to one embodiment, the filter structure is now 28 and the backplate structure 22 arranged so offset from each other, that in the contact case at most 10%, not more than 8% or at most 5% of the existing webs 104 the connection points 106 is arranged opposite and comes into contact with each other.

According to one embodiment, none of the intersections and junctions lie 104 and 106 in contact with each other. This allows the avoidance of anti-sticking elements, since already by the offset of the crossing points to each other only different webs cross each other.

A dimension of the filter structure 28 along the y- Direction may for example be a value of at least 0.5 microns and at most 5 microns, of at least 1 micron and at most 4 microns) or of at least 1.5 microns and at most 2.5 microns, for example, 2 microns. For example, a dimension of the filter pattern along the x-direction or the z-direction may have a range of at least 10 μm and at most 2000 μm, at least 100 μm and at most 1800 μm or at least 600 μm and at most 1500 μm, for example 700 μm but also have any other and especially higher values.

13d shows a schematic plan view of a section of the filter material 28 that the openings 62 that has the dimension 96 can have. The filter material 28 has the webs 98 with a lateral dimension, a land width 108 which may have the abovementioned values of at least 1 μm and at most 7 μm, at least 1.7 μm and at most 5 μm or at least 1.2 μm and at most 2 μm, for example 1.4 μm.

The 14a to 14c show schematic courses of exemplary deflections of the filter material with different configurations of the manufacturing process and / or the design of the biasing element. 14a shows influences of a generated stress, that is, a generated stress, in the filter material. A curve 112 ₁ shows a reference state in which, for example, a tensile stress is generated, that is, the biasing element generates a tensile stress in the boundary layer between the biasing element and the filter material. The curves 112 ₂ . 112 ₃ . 112 ₄ and 112 ₅ show variations in the generated stress, taking the curve 112 ₂ produces a compressive stress of 0 MPa, the curve 112 ₃ a low compressive stress of, for example, 10 MPa, the curve 112 ₄ a compressive stress of 50 MPa and the curve 112 ₅ represents a compressive stress of 100 MPa. It can be seen that with increasing compressive stress generated in the filter material, an increasing deflection of the filter structure can be obtained. For the curve 112 ₅ are in the 14b and 14c Variations in other parameters shown. So shows 14b a variation of a dimension L, for example, also in 6 is shown, and indicates how far the biasing element 32 in front of an edge region of the filter structure 28 extending toward a center region of the filter structure, that is, contraction of the biasing element from the edge. curves 114 ₁ . 114 ₂ and 114 ₃ show a respective variation in deflection along the direction y with a change in dimension L where the curve 114 ₁ a dimension L of, for example, 30 μm may show the curve 114 ₂ one dimension L of 10 μm and the dimension 114 ₃ from L equal to 3 microns. It turns out that with increasing dimension L a decreasing deflection along the y Direction is obtained. Furthermore, the bending curve with increasing dimension L steeper, which, for example, the almost crescent shape of the curve 114 ₁ becomes clear. Although the curve 114 ₃ the biggest deflection along the y Direction may allow the small dimension L may introduce a small amount of force into the filter material, which may lead to a so-called soft deformation, so that in some operating conditions, a re-deformation of the filter structure by the operating conditions. Therefore, a compromise may be, for example, to choose a deflection less than the maximum and this, however, a stable To obtain deflection, while kinks can be avoided in the bending process, as it can for example allow the dimension L = 10 microns.

14c shows in connection with the curve 112 ₅ a variation in a layer thickness of the biasing element along the y -Direction. curves 116 ₁ . ₂ and 116 ₃ show exemplary variations in the deflection along the y Direction for different layer thicknesses of the biasing element along the y Direction, where the curve 116 ₁ a dimension D of 140 nm, the curve ₂ a dimension D of 70 nm and the curve 116 ₃ indicates a dimension / thickness D of 30 nm. It can be seen that as the thickness of the biasing element decreases, increasing deflection along the y-direction can be obtained. A small material thickness can provide low stiffness, while increasing material thickness can provide additional stability, making compromises acceptable.

The total distance obtained between the structures can be selected based on the resulting acoustic influence, that is, a distance which is as small as possible and at the same time exerts a barely acceptable acoustic influence. Building on this, the dimensions of the filter structure can be chosen so that the highest possible robustness and the simplest possible processing can be obtained.

One aspect of the embodiments described herein comprises the idea of significantly removing the filter layer from the sensor by a bimorph layer structure with respect to the layer thickness of the insulation layer (layer 46 ) to deflect. This concept can be used for a variety of semiconductor sensors. An increase or optimization of the filter effect can be obtained by a high distance of the filter layer from the sensor. For this purpose, for example, an increase in the thickness of the insulating layer between the filter layer and the sensor can be obtained, for example the layer 46 ₃ in 6 , Alternatively or additionally, a high deflection of the filter layer can be used, for example, by a bimorph layer structure between the filter material and the biasing element to deflections, that is, a distance 34 to get from 10 microns and more. The bimorph structure can use layer sequences with different voltages, for example a SiN / Si layer sequence in which the SiN can have tensile stress in about 1.2 GPa and Si about 100 MPa tensile to 100 MPa compressive stress.

By arranging the additional filter structure with respect to the backplate structure, a reduction of the hole size in the filter layer can take place, whereby, however, additional influences on the acoustic behavior and thus on the sensor properties can be obtained, for example an SNR reduction. Although the arrangement of the filter structure is associated with additional expenditure for the production of the sensor, such as by deposition of the bimorph filter layer and its structuring, by a planarization of the surface after the filter layer structuring, by a deposition of the insulating layer between the filter layer and the sensor layers, by an increased time to release the layers and / or by producing anti-sticking elements for the filter layer, such as at the bottom of the lower counter electrode, significant advantages are obtained because the particles can be kept away from the sound transducer. Semiconductor-based materials for the filter material, for example silicon, silicon oxide, silicon nitride and / or silicon oxynitride, are suitable as materials. An insulation of the filter layer to the lower counter electrode is given for example in double-backplate configurations by SiN of the counter electrode. Without a filter layer, the lower counter electrode acts as a particle filter during the manufacturing process. With the use of the filter layer eliminates this requirement, therefore, taking advantage of the embodiments, the counter electrodes can be made with a larger hole diameter and thus with a better signal-to-noise ratio. For example, increasing the hole diameter from 7 microns to 10 microns can provide an SNR gain of +0.4 dB.

In some embodiments, a programmable logic device (eg, a field programmable gate array, an FPGA) may be used to perform some or all of the functionality of the methods described herein. In some embodiments, a field programmable gate array may cooperate with a microprocessor to perform one of the methods described herein. In general, in some embodiments, the methods are performed by any hardware device. This may be a universal hardware such as a computer processor (CPU) or hardware specific to the process, such as an ASIC.

The embodiments described above are merely illustrative of the principles of the present invention. It will be understood that modifications and variations of the arrangements and details described herein will be apparent to others of ordinary skill in the art. Therefore, it is intended that the invention be limited only by the scope of the appended claims and not by the specific details presented in the description and explanation of the embodiments herein.

Claims (23)

Microelectromechanical system (10; 20; 50,70; 80; 100; 110) with: a housing (12) having an access opening (14); a sound transducer structure (16) having a diaphragm structure and a backplate structure (22; 22a, 22b), the sound transducer structure (16) being coupled to the access port (14); a filter structure (26) disposed between the access port (14) and the acoustic transducer structure (16) and comprising a filter material (28) and at least one biasing element (32) mechanically connected to the filter material (28) the at least one biasing element (32) is configured to create a stress in the filter material (28) to provide bending deformation of the filter structure (26) in a direction away from the backplate structure (22; 22a, 22b). Microelectromechanical system according to Claim 1 in that the filter structure (26) is disposed between the access opening (14) and the backplate structure (22; 22a, 22b). Microelectromechanical system according to Claim 2 in that the backplate structure (22; 22a, 22b) is arranged between the membrane structure (18) and the filter structure (26). A microelectromechanical system according to any one of the preceding claims, wherein the filter material (28) and a backplate material are the same as the backplate structure (22; 22a, 22b). A microelectromechanical system according to any one of the preceding claims, wherein the filter material (28) has filter holes (62) having a first hole dimension (96), and wherein a back plate material of the back plate structure (22; 22a, 22b) has back plate holes (58) having a second hole dimension (94) which is larger than the first hole dimension. A microelectromechanical system according to any one of the preceding claims, wherein the filter structure (26) is a first hole structure having a plurality of holes (62) spaced by a plurality of first lands (98) and wherein the back plate structure (22; 22a , 22b) is a second hole structure having a plurality of second holes (58) spaced by a plurality of second lands (102), the first hole pattern and the second hole pattern being opposed and arranged such that at most 10% of the first Connecting points (104) between first webs (98) opposite to each other from second connecting points (106) between second webs (102). A microelectromechanical system according to any one of the preceding claims, wherein the filter structure (26) is a hole structure having a plurality of holes (62) spaced by a plurality of lands (98), wherein a land width (108) of the lands (98) has a value of at least 1 micron and at most 7 microns. Microelectromechanical system according to one of the preceding claims, wherein the filter structure (26) for particles (56) with a particle diameter of at least 6.5 microns is mechanically impermeable. Microelectromechanical system according to one of the preceding claims, wherein the backplate structure (22; 22a, 22b) in the edge region of the backplate structure has a first distance (64) to the filter structure (26) and in a central region has a second distance (34) has at least a double value of the first distance (64). Microelectromechanical system according to one of the preceding claims, wherein the backplate structure (22; 22a, 22b) in the edge region of the backplate structure has a distance (64) to the filter structure (26) of at most 3 microns and in a central region a distance (34) of has at least 6 microns. Microelectromechanical system according to one of the preceding claims, in which the backplate structure (22; 22a, 22b) and the filter structure (26) are firmly clamped in an edge region and an insulation material between the backplate structure (22; 22a, 22b) and the filter structure (26) (46) is arranged. Microelectromechanical system according to Claim 11 in that the filter structure (26) is exposed to the insulator material (46) to a larger extent than the backplate structure (22; 22a, 22b). Microelectromechanical system according to Claim 11 or 12 in that the insulator material (46) covers a side of the filter structure (26) facing the backplate structure (22; 22a, 22b) in a surface area to a lesser extent than a side facing away from the backplate structure (22; 22a, 22b). Microelectromechanical system according to one of the preceding claims, in which the Biasing element (32) is arranged in a filter edge region of the filter structure (26). A microelectromechanical system according to any one of the preceding claims wherein the filter material (28) comprises a polycrystalline silicon material and wherein the biasing element (32) comprises a nitride material and is disposed on a side of the filter material facing away from the backplate structure (22; 22a, 22b). A microelectromechanical system according to any one of the preceding claims, wherein the backplate structure (22; 22a, 22b) or the filter structure (26) comprises anti-sticking elements (84) disposed in a region between the backplate structure (22; 22a, 22b) and the Protrude filter structure (26). Microelectromechanical system according to Claim 16 in that the backplate structure (22; 22a, 22b) has the anti-sticking elements (84), wherein an insulating material (92) is arranged on the filter structure (26) in a region opposite to the anti-sticking elements. Microelectromechanical system according to one of the preceding claims, wherein the filter structure (26) comprises a corrugation (86). A microelectromechanical system according to any one of the preceding claims, wherein the backplate structure is a first backplate structure (22a) and the system has a second backplate structure (22b), the membrane structure (18) between the first backplate structure (22a) and the second backplate structure (22b ) is arranged. A microelectromechanical system according to any one of the preceding claims, wherein the filter structure (26) has contact areas adapted to contact the backplate structure (22; 22a, 22b) between the backplate structure (22; 22a, 22b) and the filter structure (26) in the contact areas an insulating material (92) is arranged. A microelectromechanical system according to any one of the preceding claims, wherein the filter structure (26) is adapted to reduce passage of particles (56) and / or liquid towards the backplate structure (22; 22a, 22b). Microelectromechanical system according to one of the preceding claims, which is formed as a microphone or loudspeaker. Microelectromechanical system according to one of the preceding claims, in which the filter structure (26) has an acoustic attenuation of sound transmitted or received through the access opening (14) of at most 2 dB.

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